I have got this weird issue I ran into when downgrading my migration versions in Flask using Flask-Migrate.
I have this merged head revision which happened from branching and an alembic merge heads.
"""empty message
Revision ID: 3ad527666180
Revises: ecd1f453d08e, 7112dcc79711
Create Date: 2021-11-11 12:17:31.973196
"""
from alembic import op
import sqlalchemy as sa
# revision identifiers, used by Alembic.
revision = '3ad527666180'
down_revision = ('7112dcc79711', 'ecd1f453d08e')
branch_labels = None
depends_on = None
def upgrade():
pass
def downgrade():
pass
When trying to downgrade to preceding revision which is 7112dcc79711, I get this error
docker exec -it users python manage.py db downgrade
/usr/local/lib/python3.7/site-packages/authlib/integrations/flask_oauth2/authorization_server.py:73: AuthlibDeprecationWarning: Define "get_jwt_config" in OpenID Connect grants
It will be compatible before version 1.0.
deprecate('Define "get_jwt_config" in OpenID Connect grants', '1.0')
/usr/local/lib/python3.7/site-packages/authlib/integrations/flask_oauth2/authorization_server.py:73: AuthlibDeprecationWarning: Define "get_jwt_config" in OpenID Connect grants
It will be compatible before version 1.0.
deprecate('Define "get_jwt_config" in OpenID Connect grants', '1.0')
INFO [alembic.runtime.migration] Context impl PostgresqlImpl.
INFO [alembic.runtime.migration] Will assume transactional DDL.
Traceback (most recent call last):
File "/usr/local/lib/python3.7/site-packages/alembic/script/base.py", line 227, in _catch_revision_errors
yield
File "/usr/local/lib/python3.7/site-packages/alembic/script/base.py", line 457, in _downgrade_revs
for script in revs
File "/usr/local/lib/python3.7/site-packages/alembic/script/base.py", line 454, in <listcomp>
migration.MigrationStep.downgrade_from_script(
File "/usr/local/lib/python3.7/site-packages/alembic/script/revision.py", line 798, in iterate_revisions
assert_relative_length=assert_relative_length,
File "/usr/local/lib/python3.7/site-packages/alembic/script/revision.py", line 1295, in _collect_downgrade_revisions
assert_relative_length=assert_relative_length,
File "/usr/local/lib/python3.7/site-packages/alembic/script/revision.py", line 1154, in _parse_downgrade_target
no_overwalk=assert_relative_length,
File "/usr/local/lib/python3.7/site-packages/alembic/script/revision.py", line 1069, in _walk
raise RevisionError("Ambiguous walk")
alembic.script.revision.RevisionError: Ambiguous walk
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "manage.py", line 7, in <module>
cli()
File "/usr/local/lib/python3.7/site-packages/click/core.py", line 764, in __call__
return self.main(*args, **kwargs)
File "/usr/local/lib/python3.7/site-packages/flask/cli.py", line 380, in main
return AppGroup.main(self, *args, **kwargs)
File "/usr/local/lib/python3.7/site-packages/click/core.py", line 717, in main
rv = self.invoke(ctx)
File "/usr/local/lib/python3.7/site-packages/click/core.py", line 1137, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File "/usr/local/lib/python3.7/site-packages/click/core.py", line 1137, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File "/usr/local/lib/python3.7/site-packages/click/core.py", line 956, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "/usr/local/lib/python3.7/site-packages/click/core.py", line 555, in invoke
return callback(*args, **kwargs)
File "/usr/local/lib/python3.7/site-packages/click/decorators.py", line 17, in new_func
return f(get_current_context(), *args, **kwargs)
File "/usr/local/lib/python3.7/site-packages/flask/cli.py", line 257, in decorator
return __ctx.invoke(f, *args, **kwargs)
File "/usr/local/lib/python3.7/site-packages/click/core.py", line 555, in invoke
return callback(*args, **kwargs)
File "/usr/local/lib/python3.7/site-packages/flask_migrate/cli.py", line 152, in downgrade
_downgrade(directory, revision, sql, tag, x_arg)
File "/usr/local/lib/python3.7/site-packages/flask_migrate/__init__.py", line 282, in downgrade
command.downgrade(config, revision, sql=sql, tag=tag)
File "/usr/local/lib/python3.7/site-packages/alembic/command.py", line 366, in downgrade
script.run_env()
File "/usr/local/lib/python3.7/site-packages/alembic/script/base.py", line 563, in run_env
util.load_python_file(self.dir, "env.py")
File "/usr/local/lib/python3.7/site-packages/alembic/util/pyfiles.py", line 92, in load_python_file
module = load_module_py(module_id, path)
File "/usr/local/lib/python3.7/site-packages/alembic/util/pyfiles.py", line 108, in load_module_py
spec.loader.exec_module(module) # type: ignore
File "<frozen importlib._bootstrap_external>", line 728, in exec_module
File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
File "migrations/env.py", line 87, in <module>
run_migrations_online()
File "migrations/env.py", line 80, in run_migrations_online
context.run_migrations()
File "<string>", line 8, in run_migrations
File "/usr/local/lib/python3.7/site-packages/alembic/runtime/environment.py", line 851, in run_migrations
self.get_context().run_migrations(**kw)
File "/usr/local/lib/python3.7/site-packages/alembic/runtime/migration.py", line 608, in run_migrations
for step in self._migrations_fn(heads, self):
File "/usr/local/lib/python3.7/site-packages/alembic/command.py", line 355, in downgrade
return script._downgrade_revs(revision, rev)
File "/usr/local/lib/python3.7/site-packages/alembic/script/base.py", line 457, in _downgrade_revs
for script in revs
File "/usr/local/lib/python3.7/contextlib.py", line 130, in __exit__
self.gen.throw(type, value, traceback)
File "/usr/local/lib/python3.7/site-packages/alembic/script/base.py", line 261, in _catch_revision_errors
raise util.CommandError(err.args[0]) from err
alembic.util.exc.CommandError: Ambiguous walk
What is the safe way to get past this issue?
I have tried removing one of the revisions which come from a production branch, leaving the other which tallies with my development branch and it didn't produce the error.
Is there an automatic and more feasible way to just downgrade without this issue?
